COT - Certified Ophthalmic Technician Visual Field Testing Questions and Answers — Questions and Answers
Question 1: A patient undergoing automated perimetry consistently presses the response button when no light stimulus is presented. On the Humphrey Field Analyzer printout, this will be recorded as a high number of:
- Fixation losses
- False negatives
- False positives (Correct answer)
- Pattern deviations
Correct answer: False positives
False positives occur when a patient responds (presses the button) in the absence of a light stimulus. This indicates that the patient is "trigger happy" and can compromise the reliability of the test results.
Question 2: Which of the following visual field defects is most characteristic of advanced, untreated glaucoma?
- Bitemporal hemianopia
- Central scotoma
- Altitudinal field loss respecting the horizontal midline
- Arcuate scotoma progressing to a nasal step (Correct answer)
Correct answer: Arcuate scotoma progressing to a nasal step
Glaucoma typically damages the optic nerve fibers in a characteristic pattern, often starting with an arcuate (arc-shaped) scotoma that follows the path of the nerve fiber layer. As it progresses, this can lead to a "nasal step" defect. Bitemporal hemianopia is associated with chiasmal lesions, a central scotoma with macular disease, and altitudinal loss with vascular events affecting the optic nerve.
Question 3: A technician is preparing a patient for a Goldmann visual field test. Which of the following describes the stimulus presentation method used in this type of perimetry?
- Static stimuli of varying brightness presented at fixed locations.
- A grid of vertical bars that flicker at varying rates.
- A moving light stimulus of a set size and intensity brought from non-seeing to seeing areas. (Correct answer)
- An electrical signal measurement from the retina in response to flashing lights.
Correct answer: A moving light stimulus of a set size and intensity brought from non-seeing to seeing areas.
Goldmann perimetry is the primary example of kinetic perimetry. In this method, a light stimulus of a specific size and brightness is moved from the periphery of the visual field toward the center until the patient indicates they can see it. This process maps out isopters, or areas of equal retinal sensitivity.
Question 4: During a Humphrey visual field test, the instrument checks for fixation losses by presenting a stimulus in which location?
- The foveal threshold area
- The patient's physiological blind spot (Correct answer)
- A random point in the superior visual field
- The least sensitive point from the previous test
Correct answer: The patient's physiological blind spot
The Humphrey Field Analyzer uses the Heijl-Krakau method to monitor fixation. It first maps the patient's physiological blind spot and then periodically presents stimuli within that area. If the patient responds to a stimulus in their blind spot, it indicates they have shifted their gaze from the central fixation target, and a fixation loss is recorded.
Question 5: A patient with a pituitary tumor compressing the optic chiasm would most likely exhibit which type of visual field defect?
- Homonymous hemianopia
- Bitemporal hemianopia (Correct answer)
- Central scotoma
- Unilateral vision loss
Correct answer: Bitemporal hemianopia
The optic chiasm is where the nasal retinal fibers from each eye cross over. A lesion, such as a pituitary tumor, pressing on the center of the chiasm damages these crossing fibers. This results in the loss of the temporal (outer) visual fields in both eyes, a condition known as bitemporal hemianopia.
Question 6: When instructing a patient for their first automated visual field test, which of the following is a critical instruction?
- "Only press the button for the brightest lights you see."
- "Move your eyes to look directly at each light before you press the button."
- "Keep looking at the central fixation light and press the button for any light you see, even if it's dim." (Correct answer)
- "You can take a short break and close your eyes whenever you feel tired."
Correct answer: "Keep looking at the central fixation light and press the button for any light you see, even if it's dim."
Proper patient instruction is crucial for a reliable test. The patient must maintain steady fixation on the central target throughout the test and respond to any stimulus they perceive, regardless of its brightness. Looking around for the lights results in fixation losses, and only pressing for bright lights will inaccurately map their field.
COT - Certified Ophthalmic Technician Visual Field Testing Questions and Answers
A patient undergoing automated perimetry consistently presses the response button when no light stimulus is presented.
On the Humphrey Field Analyzer printout, this will be recorded as a high number of: